1. Field of Invention
This invention relates to novel methods for preparing fluorinated organic compounds via a gas-phase reaction. In particular, the present invention relates to methods of producing fluorinated alkanes, fluorinated alkenes, and fluorocarbon polymers via a gas-phase reaction.
2. Description of Related Art
Hydrofluorocarbons (HFCs), in particular hydrofluoroalkenes such as 2,3,3,3-tetrafluoro-1-propene (R-1234yf) and hydrofluoroalkanes such as 1,1,1,2,2-pentafluoropropane (R-245cb), are known to be effective refrigerants, fire extinguishants, heat transfer media, propellants, foaming agents, blowing agents, gaseous dielectrics, sterilant carriers, polymerization media, particulate removal fluids, carrier fluids, buffing abrasive agents, displacement drying agents and power cycle working fluids. Unlike chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), both of which potentially damage the Earth s ozone layer, HFCs do not contain chlorine and thus pose no threat to the ozone layer.
Several methods of preparing hydrofluoroalkanes are known. For example, U.S. Pat. No. 6,184,426 (Belen Kill) describes a method of making R245cb via the liquid phase reaction of tetrafluoroethylene (TFE) and methyl fluoride in the presence of antimony pentafluoride catalyst. Other processes for producing hydrofluoroalkanes include those described in WO 97/02227 (DuPont) wherein carbon tetrafluoride or chloro-trifluoromethane are reacted with a fluorinated ethylene compound in the liquid phase to produce a fluorinated propane or a chlorofluorinated propane.
Methods of prepareing hydrofluoroalkenes are likewise known. For example, the preparation of R-1234yf from trifluoroacetylacetone and sulfur tetrafluoride has been described. See Banks, et al., Journal of Fluorine Chemistry, Vol. 82, Iss. 2, p. 171-174 (1997). Also, U.S. Pat. No. 5,162,594 (Krespan) discloses a process wherein tetrafluoroethylene is reacted with another fluorinated ethylene in the liquid phase to produce a polyfluoroolefin product.
However, the above-mentioned processes have a serious disadvantage in that they are salvation reactions; that is, a solvent is necessary to facilitate the reaction. Solvation reactions have a number of disadvantages. For example, certain solvents pose health risks and the risk of environmental contamination. Also, their use can dramatically increase the costs associated with synthesizing hydrofluorocarbons due to the cost of the solvent itself as well as the added expense of recovering the solvent. An additional disadvantage is the fact that the product is produced in the liquid phase instead of the gas phase. Liquid phase separation processes are substantially more difficult and costly compared to gas phase separations.
Therefore, there remains a need for methods of efficiently preparing certain hydrofluorocarbons, such as R-1234yf and R-245cb, via a gas-phase reaction. These and other needs are satisfied by the present invention.